1. Field of the Invention
The present invention is generally related to prepreg composites comprising a thermoplastic polymer and the application of such composites onto wood-containing substrates. More particularly, the present invention is generally related to unidirectional tapes comprising a thermoplastic polyester and the application of such tapes onto wood-containing materials.
2. Description of the Related Art
Composite materials have been used in the past to reinforce wood materials in various applications. Generally, these composites can contain reinforcing fibers, such as glass or carbon, which have been used to increase the strength, ductility, and stiffness of the wood materials. Such composites are capable of enhancing strength-to-weight ratios or stiffness in the wood materials, thereby enabling longer spans, smaller deflections under load, and less sag of wood.
Alternatively, metallic reinforcements, such as aluminum plates and strand cables, have also been utilized to improve the strength and stiffness of wood materials. However, these metallic materials have not been widely successful due to their relatively poor adherence to the wood substrate, the need for expensive adhesives for their application, and the mismatch in coefficient of thermal expansion between metals and woods.
Recently, particular focus has been placed on fiber-reinforced polymers (“FRP”) as a means to reinforce wood substrates. The FRPs are generally produced by impregnating reinforcing fibers with a thermoset polymer matrix. Thermoset FRPs have been utilized in various applications to reinforce wood materials since they can effectively bond to various wood substrates with the use of an adhesive and are capable of adding strength to the wood materials. Typical adhesives used for bonding FRPs to wood include epoxy resins, phenol resorcinol, formaldehyde resorcinol, melamine or cross-linked melamine, poly(vinyl acetate) (“PVA”) or cross-linked PVA, isocyanate, polyurethane, and urea-based adhesives.
While thermoset FRPs are useful in producing reinforced wood materials exhibiting enhanced strength, they do exhibit a number of deficiencies. First, the process to produce thermoset-based FRPs is very slow and can fail to meet the production needs of lumber manufacturers and distributors. A second disadvantage with thermoset FRPs is that they lack dimensional flexibility and must be prepared to specific dimensions before application. Another disadvantage with thermoset FRPs is that they require the use of adhesives to bond them onto the wood substrates, which adds costs and manufacturing complexity to produce the reinforced material. In many cases, the adhesive requires the wood and FRPs to be mechanically primed beforehand to ensure proper bonding. Consequently, this also adds to the manufacturing complexity and timeline.
Accordingly, there is a need for a wood reinforcement system for producing reinforced wood materials that can address the deficiencies of existing systems.